The present invention relates generally to an arrangement for coupling a working tool or piece of equipment, such as farm equipment, to a vehicle, such as an agricultural tractor. More particularly, the invention is directed to a coupling of the three point linkage type consisting of an upper guide member and two lower guide members which resiliently support the upper guide member. The upper guide member includes a pair of spring loaded telescopically cooperating guide elements for extension of the upper guide member. Locking jaws are provided for fixing the relative positions of the guide elements with respect to each other and a catch hook is carried at one end of the outer guide element for attachment to the working tool.
Three point linkages of a variety of types are known in the art for connecting various types of farm equipment and working tools to an agricultural tractor. The known three point linkages, however, are either difficult to manipulate in the coupling and uncoupling operation or there are disadvantages such as being unduly complicated.
One such three point linkage presently known and typical of the prior art is shown and described in German GM 7 416 431. This three point linkage has an upper guide member having an outer guide end portion, with the housing of a locking mechanism containing pivotally mounted locking jaws carried on the opposite end of the guide member. The locking jaws are annularly shaped and spring loaded so as to be urged into the annular grooves of an inner guide element to fix the longitudinal position of the upper guide member. The locking jaws are released by manipulation of guidebolts which are actuated by means of a lever. A compression spring is provided within the upper guide member for rapid length adjustment in the direction of maximum length extension. This upper guide member is supported on a resilient frame of the three point linkage to which it is articulately connected.
This type of known three point linkage has the disadvantage that the tractor driver must simultaneously watch the position of the upper catch hook, actuate a switch gear, drive the tractor, and also operate a cable for adjusting the longitudinal position of the upper guide when effecting the coupling of the tractor to a working tool. To disconnect or uncouple the working tool from the tractor, the driver must, in addition, actuate a mechanism for releasing the locking devices on the catch hooks of both the upper and lower guides.
Accordingly, it is the objective of the present invention to provide a three point linkage for facilitating and simplifying the coupling and uncoupling of a working tool with a vehicle, such as a farm tractor.
More specifically, it is an object of the present invention to provide a three point linkage which will immobilize or fix the upper guide member in its longitudinally adjusted position and lock the catch hook of the upper guide member automatically during the coupling and uncoupling maneuvers involved in attaching a working tool to a vehicle, such as a tractor.
The above objects, features and advantages, along with other objects, features and advantages of the present invention will become more apparent from the detailed description of the invention, in conjunction with the accompanying drawings to be described more fully hereinafter.